The present invention generally relates to the treatment of contaminated liquid such as water. More particularly, the present invention relates to a method of manipulation, removal or addition, and reorganization of dissolved gas volumes in a liquid, and the opportunity to efficiently irradiate the liquid, and in some instances, irradiate low pressure gas additions with photon energy through a generally evacuated low loss pathway.
In the treatment of water, it is often desirable to remove an unwanted dissolved gas, while in other treatment streams, it may be desirable to dissolve a specific gas into a solution. In addition, it is often desired to irradiate a stream of liquid with UV or other photon energies, for disinfection, sterilization, photochemical reaction and the like.
The conventional methods of gas entrainment and gas stripping in a liquid stream suffer a variety of limitations. For instance sparging of gas into a liquid is a method commonly used in low-pressure systems. The inefficiency of sparging is well known. Sparging produces gas bubbles whose excessive size causes rapid flotation out of the water, and even in systems with mechanical mixing means, most sparge gas never entrains into the liquid. Another entrainment method, pressure entrainment, has relatively slow entrainment time due to poor gas/liquid contact, and low mixing energy. In the case of dissolved gas removal, a common method uses an externally applied vacuum pump to lower the gas pressure in a partially filled liquid tank. The dissolved gas is flashed out of solution and then the gas is transferred, utilizing the pump, to a gas scrubber or the like. As gas is removed, its removal rate is limited by the diffusion rate through the liquid. Due to a vacuum forming over a liquid body, and long diffusion time required to degas the liquid, an appreciable amount of the liquid itself may undesirably be evaporated as well.
When photon irradiation of a liquid is desired, conventional devices place UV lamps inside protective sleeves, which assemblies are then immersed in the treatment stream wherein the liquid flows around the tubes. International Publication WO94/02680 entitled HydroCyclone Photo-Reactor discloses such a system. Additionally, U.S. Pat. No. 5,439,595 to Downey, Jr. discloses a similar system wherein UV light is emitted through lenses which are in direct contact with the waste liquid. Well known limitations of these methods are fouling of the lamp protective sleeves, causing low exposure efficiency, and poor positioning of the target contaminates in the liquid solution, causing obscuration or “shadowing” of target organisms and other contaminants in the generally laminar stream flow. This “shadowing” prevents the photon energy reaching desirably irradiated features of the solution, e.g. undesirable microorganisms, toxic compounds and the like. Further, operating efficiency suffers with low energy mixing of the irradiated liquid, wherein the target species are less likely to be positioned into a high photon flux density near the photon source, thus requiring longer exposure times for a given desired photon flux density.
Accordingly, what is needed is an apparatus and method to overcome poor gas transfer rates, low mixing energy, and excessive treatment times provided by the prior art. What is also needed, is a means of photon irradiation of a liquid to maximize photon dose to all liquid constituents while minimizing system power requirements. What is further needed, is a means of in-situ photon irradiation of a low-pressure gas such as oxygen allowing direct ozonation and ingestion into a liquid such as water. The present invention fulfills these needs and provides other related advantages.